The present invention relates to a package strapping machine for tightening a thermoplastic synthetic resin tape looped around a package to bind the package, particularly to a package strapping machine suitable for tying a package into a circular shape.
Automatic package strapping machines using a thermoplastic tape have been widely used for packaging various kinds of articles, because of their efficiency and labor saving operation. A tape is drawn out from a reel, wound around a package, tightened, and then both ends of the tape are heated and pressed to weld them together. Thus the package is automatically and closely tied.
According to the conventional package strapping machine, as shown in FIG. 5, a first clamp 2, a press 3 and a second clamp 4 are disposed side by side, immediately below a base 1 placed on an upper cover 11 of a table, so that they may move up and down. A thermoplastic tape A is drawn out from a reel 5 onto the table from between the second clamp 4 and the base 1 through a tape delivery and tightening mechanism 6 and a feed hole 7 of the first clamp 2. A leading end of the tape A is wound around a package B on the base 1, and is then inserted below the base 1. The first clamp 2 moves up by means of a cam mechanism 8 driven by a motor M, clamping the leading end of the tape A between the first clamp 2 and the base 1. Subsequently, after tightening the tape A by means of the mechanism 6, the second clamp 4 is moved up to clamp the inserted end and a trailing end of the tape A between the second clamp 4 and the base 1. Then the press 3 is moved up to cut the tape A with a cutting mechanism disposed between the press 3 and the first clamp 2. A heater enters a space between the upper tape and the lower tape immediately above the press 3, and the press 3 is moved up to press opposite upper and lower faces of the tape A together with the heater therebetween. The opposite upper and lower faces of the tape A are continued to be pressed together by the press 3 after the heater is withdrawn to weld them together.
Immediately after the tape is welded, both clamps 2, 4 and the press 3 are lowered, and the base 1 is drawn out from the space between the tape and the package B to finish the packaging process. At this point the tape delivery and tightening mechanism 6 is again operated to deliver another length of the tape A above the base 1. The machine is then prepared for the next packaging process.
However, the base 1 in the conventional package strapping machine, as shown in FIG. 5, has a flat upper surface. When a package is to be tied into a circular shape, as in bundles of articles such as flowers and wires, the use of a flat base has poor results. Not only is the operation difficult to carry out, but the overall length of the tape extending over the base 1 and the package B is much longer than necessary. This leaves little tension in the tape after the packaging process is completed. As a result, a strong tightly-bound packaged condition cannot be obtained.
In addition, when the package is removed from the base 1 after the completion of the welding of the tape, the base must be withdrawn through the space between the package and the tape.
If the tightening force of the tape wound around the package and the base is increased in order to create a more tightly bound package, a disadvantage occurs. The tape will tightly hold the package to the base, and be moved together with the base when the base is withdrawn, thus preventing removal of the base.